The Theory And Application Of Refining Regional Geoid

With the recent advance in GPS technique, direct transformation from GPS-derived ellipsoidal heights to orthometric heights or normal heights in centimeter level becomes inevitable. Its implement can produce direct economic benefits by tremendously reducing laborious field tasks so as to increase efficiency. However, the precondition of realizing this goal is to determinate an accurate geoid or quasi-geoid. Currently, regional geoid or quasi-geoid determination with centimeter level is the focus of geodesy research, it will provide mufti-disciplinary research and application such as base map up date, digital China geo-spatial framework, regional monitoring on settlement, earth science research, traffic, water conservancy and electric power with essential mapping service.To begin with, the article analyses the importance of refining regional geoid and its developments in China and abroad. Then it studies systematically the basic theories and principles of refining regional geoid and digs into the methods of gravity and geometer respectively. In the gravity method, it describes the theories and techniques in determining a precise regional geoid, the computing model of geoid, means of determining regional centimeter rank accurate geoid. In the geometrical method, it introduces three methods, astronomy leveling, satellite altimetry and GPS/leveling. It especially describes GPS/leveling fitting methods: figure fitting, curve fitting (multinomial curve fitting, cubic sp line curve fitting and Akima curve fitting) and curved surface fitting (multinomial curved surface fitting, moving curved surface fitting, Hardy function interpolation fitting and SP function fitting). Besides, it also describes the method of integrating fitting and global geopotential model. Combining measuring region GPS/leveling data thesis adopts the multinomial surface fitting model and move curve surface fitting model and Hardy function interpolation model, author has developed a VB program to do the test and analyze its accuracy and draws several satisfied conclusions. The fitting regional quasi-gieod can be applied into the shift between GPS height and normal height. Then, it introduces the theory of global geopotential model and studies how to determine regional quasi-geoid with remove～restore method, GPS/leveling data and global geopotential model, gaining the normal height at last. Based on the comparison, its feasibility is also analyzed.At last, it analyzes the error resources of regional geoid refining and summarizes how to choose a proper method in different conditions.